1. Field of the Invention
The present invention relates to a unit for controlling the discharge of molten metal in a substantially downward direction from a metallurgical vessel, which unit includes a valve comprising a refractory stator fixed to refractory lining of the metallurgical vessel, and a refractory rotor disposed in the stator and being longitudinally slidable and/or rotatable relative to the stator for opening or closing the valve. When the unit is in place in the metallurgical vessel, the valve projects into the molten metal within the vessel. The valve defines a discharge opening therein open at one side of the refractory lining of the metallurgical vessel and flow control passageways which may place the interior of the metallurgical vessel in communication with the discharge opening so that molten metal may be discharged through the valve from the metallurgical vessel.
2. Description of the Related Art
U.S. Pat. No. 3,651,998 discloses a valve of the aforementioned type comprising a stator fixed to the refractory lining of a metallurgical vessel and extending into the vessel, and a rotatable rotor mounted concentrically in the stator. The rotor is forced against a closed top end of the stator by springs exerting a force on the bottom of the rotor. When the valve is open, molten metal flows through several transverse passageways into a central discharge opening defined in the rotor and then out of the valve. Since a relatively large clearance is provided between the rotor and the stator, the gap formed between the rotor and the stator can hardly prevent molten metal from flowing between the stator and the rotor even when gas is introduced into the gap. Molten metal passing between the rotor and the stator can harden very rapidly and cause the rotor to jam. Furthermore, a tensile force exerted on the stator by the springs via the rotor is undesirable since the refractory material of the stator can withstand only small tensile forces and is, moreover, somewhat weak due to a plurality of transverse flow control passageways extending therethrough.
A valve for controlling the discharge of molten metal from a metallurgical vessel is also disclosed in DE-PS 35 40 202 and comprises two concentric pipes. The inner pipe extends through a discharge opening in the vessel and the outer pipe is slidingly fitted over the inner pipe. The inner and outer pipes each have a flow control passageway extending therethrough. By rotating and moving the outer pipe longitudinally relative to the inner pipe, the flow control passageways of the pipes can be aligned to discharge the molten metal from the vessel in a controlled manner. In such a valve, a relatively expensive mechanism above the vessel is required to rotate the outer pipe. Such a mechanism cannot exert any transverse forces on the outer pipe without risking the possibility of the inner pipe breaking. If the metallurgical vessel is an intermediate vessel, space conditions are usually quite restricted due to the disposition of a ladle directly above the intermediate vessel, such an arrangement being undesirable.